exceedingly large chess set


I have a set with a 7" king with a 2" base and the board has 3" squares. The tabletop is 28" square.
I think your calculation is probably off.
/ What is the base diameter of the pieces?
https://www.chessbazaar.com/blog/2016/02/01/how-to-find-the-right-size-chessboard-for-your-wooden-chess-pieces/
Says that the squares should be 4/3 of the king base. So if your pieces have a king with a 3" base, the squares should be 4" or only 2' 8" for the actual playing surface- so a 3 foot table would likely suffice. (You need space for resting pieces, clocks, coffee cups, arms, etc.)
See also: https://www.chess.com/forum/view/chess-equipment/a-system-for-sizing-chess-pieces-and-boards-long

I was going based off liking to be able to fit 4 pawns to a square so was envisioning 6" squares. But as you suggested I was a bit generous. The bases of the pawns are 2 5/8" so that would shave a few inches off. if I went with 4/3 of the king's base I would get 4" squares giving me around a 40"board if I include a boarder.

A table top board needs to be comfortable for the players. If you use 6" squares you could play with a set of these.
https://www.amazon.com/RMS-Grabber-Reacher-Rotating-Gripper/dp/B07PHKY2JW/ref=sr_1_9?crid=3NB11E463C5OK&keywords=extension+grabbers+tool+to+pickup+extra+long&qid=1579538473&sprefix=extension+grabbers%2Caps%2C208&sr=8-9
lol